JP6292052B2 - Image characteristic measuring device, image evaluation device, image forming device - Google Patents

Description

  The present invention relates to an image characteristic measurement device, an image evaluation device, and an image forming device.

  In recent years, in the field of production printing, digitization of both sheet-fed machines and continuous book machines has progressed, and many products such as electrophotographic systems and inkjet systems have been put on the market. As user needs shift from monochrome printing to color printing, multi-dimensional images and high-definition and high-density printing are promoted, high-quality photo printing, catalog printing, and advertisements that respond to individual preferences for invoices, etc. With the diversification of service forms that can be delivered to customers, the demand for high image quality and color reproduction is also increasing.

  As a technology that supports high image quality, the electrophotographic system is equipped with a density sensor that detects the toner density before fixing on the intermediate transfer member and photoconductor to stabilize the toner supply amount. Regardless of the method, the output image is captured by a camera or the like and inspected by character recognition or difference detection based on the difference between images. For color reproduction, a color patch is output, and one or more color measurements are performed with a spectrometer. Things to do have been put on the market. These techniques are preferably performed with the full width of the image to accommodate image variations between pages and within a page.

  As an image characteristic measuring apparatus for measuring the color of the full width of an image, for example, an apparatus provided with a mechanism for arranging a plurality of line-shaped light receiving elements and moving a measurement object relative to a detection system is known. This image characteristic measuring apparatus includes a light shielding wall in order to prevent crosstalk of reflected light from a detection target region between light receiving elements during measurement (see, for example, Patent Document 1).

  However, in the conventional image characteristic measuring apparatus, the relative position and relative posture with respect to the object (paper or the like) for measuring the color of the full width of the image depend on the mechanical positioning on the drawing. Variations in the reflection layout due to variations in the shape of the object due to the above are problematic. For example, even if an object is conveyed while being pressed by a roller in an image evaluation apparatus or an image forming apparatus equipped with an image characteristic measuring apparatus, the front and rear end portions of the object are not pressed by the roller, but have a shape change timing. Therefore, it is difficult to measure the color of the front and rear end portions of the object with high accuracy.

  On the other hand, it is not rational to install sensors (line sensors, etc.) at two locations in order to cope with only measurement of the front and rear end portions of the object, and space is also a problem. For this reason, there is no image characteristic measuring apparatus that measures the color of the entire image width with high accuracy and further measures the color of the front and rear end portions of the object with high accuracy.

  The present invention has been made in view of the above points, and measures the color of the entire image width with high accuracy, and further measures the color of the front and rear end portions of the object with high accuracy with a single sensor. Etc. to be provided.

The image characteristic measurement apparatus includes: a light irradiating unit that irradiates light on an object; a first image forming unit that collects reflected light from the object irradiated from the light irradiating unit; The reflected light from the object condensed by the first imaging means is divided into regions by a plurality of openings, and the reflected light from the object that has been divided into regions through the openings is reflected. A second imaging means for condensing; a spectroscopic means for spectroscopically reflecting the reflected light from the region-divided object collected by the second imaging means; A light receiving means for receiving reflected light from the object, and the plurality of openings include a first opening not provided with an optical path changing means on the object side for changing an optical path of the incident light, and incident light. The optical path changing means for changing the optical path of the object is provided on the object side. Seen including a neck, a light reflected from the first region of the object passes through the first opening, the reflected light from the second region of the object changes the optical path by the optical path changing means And passing through the second opening .

  According to the disclosed technology, it is possible to provide an image characteristic measuring device or the like that measures the color of the entire image width with high accuracy, and further measures the color of the front and rear end portions of the object with high accuracy with a single sensor.

It is a figure which illustrates the image characteristic measuring device concerning a 1st embodiment. It is a figure which expands and schematically illustrates a part of FIG. It is the photograph (the 1) which shows the state which looked at the incident light to a line sensor from the incident surface side. It is a figure explaining the crosstalk exclusion of a diffraction image. It is the photograph (the 2) which shows the state which looked at the incident light to a line sensor from the incident surface side. It is a figure which illustrates the spectral distribution of the toner image used for simulation. It is a figure which illustrates a simulation result. It is a figure explaining the relationship between the angle of the light which injects into a diffraction element, and diffraction performance. It is FIG. (1) explaining an aperture array and an optical path changing means. It is FIG. (2) explaining an aperture array and an optical path changing means. It is a figure which illustrates the image evaluation apparatus which concerns on 1st Embodiment. It is a figure explaining the timing of conveyance of an image carrier medium, and spectroscopic measurement. It is a figure which illustrates the image characteristic measuring device which concerns on the modification of 1st Embodiment. It is a figure which illustrates the image characteristic measuring device which concerns on 2nd Embodiment. It is a figure which illustrates the image forming apparatus which concerns on 3rd Embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
FIG. 1 is a diagram illustrating an image characteristic measuring apparatus according to the first embodiment. Referring to FIG. 1, an image characteristic measuring apparatus 10 includes a line illumination light source 11, an imaging optical system 12, an aperture array 13, an imaging optical system 14, a diffraction element 15, a line sensor 16, and a line. An illumination light source 21, an imaging optical system 22, and a mirror 23 are included. Reference numeral 90 denotes an image bearing medium (paper, cloth, etc.) that is a measurement object.

  The image characteristic measuring apparatus 10 and the image bearing medium 90 are configured to be relatively movable. The direction parallel to the direction in which both of the image characteristic measuring apparatus 10 and the image bearing medium 90 relatively move is the X axis, and the normal direction of the image bearing medium 90 is Z. The direction perpendicular to the axis, the X axis, and the Z axis is taken as the Y axis.

In the image characteristic measuring apparatus 10, the imaging optical system 12, the aperture array 13, the imaging optical system 14, the diffraction element 15, and the line sensor 16 are light applied to the line 91 of the image bearing medium 90 from the line illumination light source 11. diffuse reflected light L ₁₁ of which constitutes a first optical path to propagate.

Further, the imaging optical system 22, the mirror 23, the aperture array 13, the imaging optical system 14, the diffraction element 15, and the line sensor 16 diffuse the light emitted from the line illumination light source 21 to the line 92 of the image bearing medium 90. reflected light L ₂₁ constitute a second optical path that propagates. The line 91 and the line 92 are at different positions on the X axis and are parallel to the Y axis.

  First, the first optical path will be described. In the optical system constituting the first optical path, light emitted from the line illumination light source 11 is incident on the image bearing medium 90 at an angle of approximately 45 degrees, and the line sensor 16 is diffusely reflected from the image bearing medium 90 in the vertical direction. This is a so-called 45/0 optical system that receives light.

  However, the optical system constituting the first optical path is not limited to that illustrated in FIG. In the optical system constituting the first optical path, for example, the light emitted from the line illumination light source 11 is perpendicularly incident on the image carrier medium 90 and the line sensor 16 diffuses from the image carrier medium 90 in a 45 degree direction. A so-called 0/45 optical system that receives light may be used.

  The line illumination light source 11 has a function as light irradiation means for irradiating light in a line shape in the width direction (Y direction) of the image bearing medium 90. As the line illumination light source 11, for example, a white LED (Light Emitting Diode) array having an intensity in almost the entire visible light region can be used.

  A lamp light source such as a fluorescent lamp such as a cold cathode tube or a xenon lamp may be used as the line illumination light source 11, but in particular, when an image moving at a high speed is to be measured, It is preferable to use a white LED array having high brightness. However, it is preferable that the line illumination light source 11 emits light in a wavelength region necessary for spectroscopy and can be illuminated uniformly over the entire observation region. The line illumination light source 11 may have a cylindrical lens or the like.

The imaging optical system 12 has a function for converging the diffused reflected light L ₁₁ of the light emitted from the line illumination light source 11 to the image carrying medium 90. More specifically, the imaging optical system 12, the diffuse reflection light L ₁₁ of the light irradiated to the image carrying medium 90, is temporarily imaged in the aperture array 13 by adjusting the magnification. The imaging optical system 12 can have a configuration similar to, for example, a scanner lens including a plurality of lenses. The imaging optical system 12 is a typical example of the first imaging unit according to the present invention.

Aperture array 13 has a function as area dividing means for dividing the diffuse reflected light L ₁₁ of the light irradiated to the image carrying medium 90 into a plurality of regions. The aperture array 13 has, for example, a structure in which a plurality of apertures through which light passes are arranged in a row in a light shielding portion. Specifically, as the opening array 13, a metal plate subjected to blackening treatment is provided with a plurality of holes, or a black member such as chromium or carbon-containing resin is formed in a predetermined shape on a glass substrate Etc. can be used. In the opening array 13, the shape of each opening can be circular or rectangular, but is not limited thereto, and may be, for example, an ellipse or other shapes.

  One aperture of the aperture array 13 corresponds to one spectral sensor (described later), and one aperture and N pixels of the spectral sensor are in an imaging relationship. Furthermore, a plurality of openings and N pixels are formed and arranged in one direction, so that a spectral sensor array in which spectral sensors are arranged in one direction can be formed on the line sensor.

The imaging optical system 14 has a function of condensing the diffusely reflected light L <b> ₁₁ that has been divided into regions through each aperture of the aperture array 13. More specifically, the imaging optical system 14 can be composed of, for example, a plurality of lenses, and adjusts the magnification, telecentricity, and optical axis direction of each image divided into a plurality of regions by the aperture array 13 and performs diffraction. An image is formed (condensed) on the line sensor 16 via the element 15. As the imaging optical system 14, for example, a microlens array, a Selfoc lens array (registered trademark), or the like can be used. The imaging optical system 14 is a typical example of the second imaging unit according to the present invention.

  The diffractive element 15 has a function as a spectroscopic unit that divides each of the divided images collected by the imaging optical system 14. The diffraction element 15 causes light having different spectral characteristics to enter a plurality of pixels of the line sensor 16. As the diffraction element 15, for example, a transmission type grating or the like can be used.

  The line sensor 16 is composed of a plurality of pixels, and has a function as a light receiving means for receiving each of the divided images obtained by the diffraction element 15. That is, the line sensor 16 can acquire the amount of diffusely reflected light in a predetermined wavelength band incident via the diffraction element 15. As the line sensor 16, for example, a metal oxide semiconductor device (MOS), a complementary metal oxide semiconductor device (CMOS), a charge coupled device (CCD), or the like can be used.

  FIG. 2 is a diagram schematically illustrating a part of FIG. 1 in an enlarged manner. As shown in FIG. 2, the light flux from each aperture of the aperture array 13 is dispersed by the diffractive element 15, and the intensity of a plurality of wavelength bands can be acquired by a plurality of pixels of the line sensor 16 (7 pixels in the example of FIG. 2). Become. The diffractive element 15 in FIG. 2 is arranged close to the line sensor 16, and the N light beams of the line sensor 16 are diffracted by diffracting the incident light as schematically shown by the broken line in FIG. Light having different spectral characteristics is incident on the pixels (seven pixels in the example of FIG. 2).

  As the diffraction element 15, for example, an element in which a sawtooth structure is periodically formed on a transparent substrate can be used. Assuming that the period of the sawtooth portion of the diffraction element 15 is p, light having a wavelength λ incident on the diffraction element 15 at an angle α is diffracted to an angle θm expressed by the equation (Equation 1). In the equation (Equation 1), m is the order of the diffraction grating, and can be a positive or negative integer value.

By making the shape of the diffraction element 15 into a sawtooth shape as shown in FIG. 2, it is possible to increase the intensity of the + 1st order diffracted light, which is most desirable. However, the diffraction element 15 can have a stepped shape in addition to the sawtooth shape. If the pixel period d of the line sensor 16 is 10 μm, the visible light is reduced to about 6 pixels when the period p of the diffraction element 15 is 10 μm and the distance between the diffraction part of the diffraction element 15 and the line sensor 16 is 2 mm. It is possible to enter by spectroscopic.

  However, when diffracted in the arrangement direction of the elements of the line sensor 16 (Y direction in FIG. 1), diffraction images of non-diffracted light (0th order light), −1st order light, + 2nd order light, −2nd order light, etc. As shown in FIG. 3, they overlap on the sensor and cause crosstalk, making it difficult to obtain accurate spectral characteristics.

  Therefore, in order to block diffracted light other than the desired order, the diffractive element 15 is rotated in a plane perpendicular to the optical axis (Z-axis direction) of the optical system in FIG. Set to a predetermined value. As a result, as shown in FIG. 4, it is possible to eliminate the crosstalk of the diffraction image and acquire the intensity of each wavelength band.

  In FIG. 4, the line sensor 16 has a pixel structure in which a plurality of pixels are arranged in a line in the Y direction. The line sensor 16 constitutes a spectroscopic sensor array in which a plurality of spectroscopic sensors 16a, 16b, 16c, and the like, each having a group of N pixels arranged in parallel in the Y direction, are arranged in the Y direction. In FIG. 4, diffracted images of non-diffracted light (0th order light) A, −1st order light C, + 2nd order light D, −2nd order light E, etc. are excluded, and each spectroscopic sensor acquires only + 1st order light B. doing.

  FIG. 5 shows the diffraction element 15 in which the diffraction direction of the diffraction element 15 is in a plane (XY plane) perpendicular to the optical axis (Z direction) of the entire optical system, and N pixels of the line sensor 16 are arranged. This is an example in the case of being arranged so as to be inclined by 10 [deg] with respect to the direction (Y direction). The optimum tilt angle can be determined from conditions such as optical elements and layout.

  For color measurement in the visible range, diffraction performance from about 350 nm to about 780 nm is required, and of course, a diffraction image can be acquired by setting the grating frequency and blaze angle of the diffraction element 15. In addition, although the peak diffraction efficiency is somewhat lower than that of the sawtooth diffraction grating, it is possible to secure a certain diffraction performance in a wide wavelength region in the visible region and outside the visible region by applying the holographic diffraction grating. .

  When acquiring color information of an image formed with color toner by the image characteristic measuring apparatus 10, a set of elements constituting a spectroscopic measurement system in the visible range on the line sensor 16 in a wavelength range of about 400 nm to 700 nm. Thus, a multiband spectroscopic sensor is configured. In multiband spectroscopy, the more the number of bands N, the more detailed measurement results of the spectral distribution can be obtained, which is preferable.

  However, when the number of pixels of the line sensor 16 is constant, the number of spectral sensors that can be arrayed decreases as the number of bands (number of N) increases. Therefore, it is preferable that the image characteristic measurement apparatus 10 includes processing (spectral estimation processing) in which the spectral distribution is estimated by estimation means such as Wiener estimation while minimizing the number of bands. Many methods have been proposed for spectral estimation processing, and details are described in, for example, “Analysis and Evaluation of Digital Color Images: University of Tokyo Press: p154-p157” which is a non-patent document.

  An example of a technique for estimating the spectral distribution from the output vi from one spectroscopic sensor is shown below. From the row vector v storing the signal outputs vi (i = 1 to N) from the N pixels constituting one spectroscopic sensor and the conversion matrix G, the spectral reflectance (for example, 400 to 700 nm) of each wavelength band. The row vector r storing 31 of 10-nm pitch is expressed by the equation (Equation 2).

The transformation matrix G can be obtained as shown in Equation (Equation 3) to Equation (Equation 5). That is, from a matrix R storing spectral distributions for a large number (n) of samples whose spectral distributions are known in advance, and a matrix V storing v when similar samples are measured by this measuring apparatus, the least square method is used. Can be obtained by minimizing the square norm of error ‖ · ‖2.

A transformation matrix G, which is a regression coefficient matrix of a regression equation from V to R, where V is an explanatory variable and R is an objective variable, is expressed using a Moore-Penrose generalized inverse matrix that gives a squared least norm solution of the matrix V. It is calculated as (Equation 6).

Here, the superscript T represents the transpose of the matrix, and the superscript -1 represents the inverse matrix. By storing the conversion matrix G obtained in this way, the spectral distribution r of an arbitrary object to be measured is estimated by taking the product of the conversion matrix G and the signal output v during actual measurement.

  As an example, a simulation is performed in which a toner image output by an electrophotographic image forming apparatus is read by the spectral sensor array according to the present embodiment, a spectral distribution is estimated, and a color difference that is an estimation error is calculated from the estimated spectral distribution. went. In the simulation, the color difference (ΔE) between the color measurement result when the value of N is changed and the color measurement result obtained from a more detailed spectroscopic device is obtained.

  FIG. 6 is a diagram illustrating the spectral distribution of the toner image used in the simulation. FIG. 7 is a diagram illustrating a simulation result. FIG. 7 shows that there is no significant difference in the estimated value error when N is 6 or more. That is, by setting the number of pixels required for each spectroscopic sensor at each position to be 6 or more, although there is a difference in accuracy between the spectroscopic sensors, it is possible to perform spectroscopic measurement with high accuracy over the entire area.

As shown in FIG. 8, if the angles of the light L ₁ , L ₂ , and L ₃ incident on the diffraction element 15 are different, the diffraction images D ₁ , D ₂ , and D ₃ are also propagated at different angles, respectively. Chromatic aberration will occur at the time of image formation on the line sensor. In FIG. 8, S ₁ indicates the diffractive surface of the diffractive element 15, S ₂ indicates the image plane when the diffractive element 15 is present, and S ₃ indicates the image plane when the diffractive element 15 is not present.

Therefore, it is desirable that the imaging optical system 12 is image side telecentric. When the imaging optical system 12 is image-side telecentric, the angle of light that passes through the aperture array 13 and the imaging optical system 14 and enters the diffraction element 15 becomes vertical. That is, in FIG. 8, the light L ₁ , L ₂ , and L ₃ are incident on the diffraction element 15 perpendicularly.

Thereby, in FIG. 8, the diffraction images D ₁ , D ₂ , and D ₃ also propagate at the same angle, and no chromatic aberration occurs at the time of image formation on the line sensor, and the diffraction performance of each spectroscopic sensor is reduced. It can be made uniform.

  Note that by bonding the aperture array 13, the imaging optical system 14, the diffractive element 15, and the line sensor 16 to each other, it becomes possible to eliminate the relative positional deviation of the optical element due to vibrations in the external environment, and is resistant to vibrations. An optical system can be realized.

  Returning to FIG. 1, the second optical path will be described. In the optical system constituting the second optical path, the light emitted from the line illumination light source 21 enters the image bearing medium 90 at an angle of approximately 45 degrees, and the line sensor 16 diffuses and reflects from the image bearing medium 90 in the vertical direction. This is a so-called 45/0 optical system that receives light.

  However, the optical system constituting the second optical path is not limited to that illustrated in FIG. In the optical system constituting the second optical path, for example, the light emitted from the line illumination light source 21 enters perpendicularly to the image carrier medium 90, and the line sensor 16 diffuses from the image carrier medium 90 in a 45 degree direction. A so-called 0/45 optical system that receives light may be used.

  The line illumination light source 21 has a function as light irradiation means for irradiating light in a line shape at a position different from the line irradiated by the line illumination light source 11 in the width direction (Y direction) of the image bearing medium 90. As the line illumination light source 21, for example, the same type of light source as the line illumination light source 11 can be used.

The imaging optical system 22 has a function as an imaging unit that temporarily images the diffuse reflected light L ₂₁ of the light irradiated on the image bearing medium 90 on the aperture array 13 by adjusting the magnification. The imaging optical system 22 can have a configuration similar to, for example, a scanner lens including a plurality of lenses. The light transmitted through the imaging optical system 22 has its optical path converted by the mirror 23 (for example, the optical path is converted by 90 °), and then temporarily forms an image on the aperture array 13.

  In the second optical path, the aperture array 13, the imaging optical system 14, the diffraction element 15, and the line sensor 16 are common to the first optical path. However, the aperture array 13 needs to have a special structure because light enters from different directions in the first optical path and the second optical path.

The opening array 13 can be configured as shown in FIG. 9, for example. As shown in FIGS. 9A to 9C, the plurality of openings 130 (five in the example of the figure) of the opening array 13 have the same shape, but the first is not provided with the micromirror 24 immediately below. an opening 130 _1, and a second opening 130 ₂ which is provided with a micro mirror 24 immediately below.

The optical path converted diffuse reflected light L ₂₁ enters further into the second opening 130 ₂ is converted to the optical path in the micro mirror 24 by a mirror 23, the line sensor 16 through the imaging optical system 14 and the diffraction element 15 Reach. Further, the inclined surface of the micro mirror 24 is formed of, for example, a metal film (reflection film), diffuse reflected light L ₁₁ that reaches the inclined surface of the micro mirror 24, reflected in a direction not incident to the second opening 130 ₂ Is done. The micromirror 24 is a typical example of the optical path changing means according to the present invention.

The first opening 130 ₁ which is not provided with the micro mirror 24, the diffuse reflection light L ₂₁ does not enter because they are not converted to the optical path. On the other hand, the diffuse reflection light _{L 11} is first incident on the aperture 130 ₁ goes straight, reaches the line sensor 16 through the imaging optical system 14 and the diffraction element 15.

That is, in the aperture array 13, the diffuse reflected light L ₁₁ is incident on the first opening 130 ₁ , and the diffuse reflected light L ₂₁ is incident on the second opening 130 ₂ . Neither diffusely reflected light L ₁₁ nor L ₂₁ is incident on the same aperture. As a result, two optical axes of the line sensor 16 can be obtained. That is, it becomes possible to simultaneously acquire diffuse reflected light at two different positions (two lines) on the image bearing medium 90.

  In the image characteristic measuring apparatus 10, if both the image sides of the imaging optical systems 12 and 22 are telecentric, the optical path length between the aperture array 13 and the imaging optical systems 12 and 22 can be flexibly taken. The layout of the system becomes easy.

Incidentally, it is preferable to regularly distributed first opening 130 ₁ and the second opening 130 _2. For example, as shown in FIG. 10, diffuse reflection at by arranging the first opening 130 ₁ and the second opening 130 ₂ alternately, different positions alternately spectroscopic sensor adjacent (another line) Light can be acquired.

  FIG. 11 is a diagram illustrating an image evaluation apparatus according to the first embodiment. Referring to FIG. 11, the image evaluation device 50 includes an image characteristic measurement device 10, a belt 51, a front roller 52, and a rear roller 53. For example, the image evaluation device 50 calculates the color measurement data such as XYZ and L * a * b * by synthesizing the outputs from the image characteristic measurement device 10, and the image formed on the image carrier medium 90 in a plurality of colors. It is possible to have the function of evaluating the color of

  The image evaluation apparatus 50 may include image evaluation means including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a main memory, and the like. In this case, various functions of the image evaluation means can be realized by reading a program recorded in the ROM or the like into the main memory and executing it by the CPU. However, part or all of the image evaluation means may be realized only by hardware. The image evaluation unit may be physically configured by a plurality of devices.

  In the image evaluation apparatus 50, the belt 51 is a typical example of a moving unit that relatively moves the image characteristic measurement apparatus 10 and the image bearing medium 90 in a predetermined direction (for example, the X direction). The front roller 52 and the rear roller 53 are typical examples of pressing means for pressing the front side and the rear side of the image bearing medium 90 in a predetermined direction (for example, the X direction).

  As shown in FIG. 12, in the image evaluation apparatus 50, the image carrying medium 90 placed on the belt 51 is conveyed in the arrow direction (sub-scanning direction) while being sandwiched between the front roller 52 and the rear roller 53 ( In FIG. 12, illustration of the image characteristic measuring apparatus 10 is omitted). A and B indicate two measurement positions (two lines) on the image bearing medium 90. That is, A and B correspond to the lines 91 and 92 in FIG.

  The image evaluation device 50 measures the color of the image when the front side and the rear side of the image bearing medium 90 are both pressed by a roller or the like. This will be described in detail with reference to FIG.

  As shown in FIG. 12A, the image characteristic measurement device 10 of the image evaluation device 50 does not perform measurement in a state where the front end portion of the image carrying medium 90 is not pressed by the front roller 52. This is because in the state where the front end portion of the image carrying medium 90 is not pressed by the front roller 52, the shape (deflection, warpage, etc.) of the front end portion of the image carrying medium 90 is unknown, so high-precision spectroscopic measurement cannot be expected. Because.

  Next, as shown in FIG. 12B, measurement is started at measurement positions A and B immediately after the front end portion of the image bearing medium 90 is pressed by the front roller 52. In this state, the front end portion of the image bearing medium 90 is pressed by the front roller 52, and the rear side of the front end portion of the image bearing medium 90 is pressed by the rear roller 53, so that the image is measured at the measurement positions A and B. Since the carrier medium 90 is flat, high-precision spectroscopic measurement is possible.

  Then, as shown in FIG. 12C, the measurement positions A and B are maintained while the front side of the image bearing medium 90 is pressed by the front roller 52 and the rear side of the image bearing medium 90 is pressed by the rear roller 53. Continue measurement at.

  Further, as shown in FIG. 12D, the measurement is continued at the measurement positions A and B until immediately before the rear end portion of the image bearing medium 90 is separated from the rear roller 53, and as shown in FIG. Measurement is not performed in a state where the rear end portion of the image bearing medium 90 is not pressed by the rear roller 53. This is because in the state where the rear end portion of the image bearing medium 90 is not pressed by the rear roller 53, the shape of the rear end portion of the image bearing medium 90 (whether warpage or the like has occurred) is unknown. This is because spectroscopic measurement cannot be expected.

  The image evaluation apparatus 50 is provided in the conveyance path of the image carrier medium 90 at the moment when the front end portion of the image bearing medium 90 is pressed by the front roller 52 and the moment when the rear end portion is separated from the rear roller 53. It can be recognized based on information of a sensor that detects the passing position of the image bearing medium 90.

  Eventually, as shown in FIG. 12F, the region indicated by a on the upper surface of the image bearing medium 90 can be spectroscopically measured based on the measurement value at the measurement position A, and the region denoted by b on the image bearing medium 90 is The spectroscopic measurement can be performed based on the measurement value at the measurement position B. Further, in the region indicated by c on the image bearing medium 90, by combining the measurement values at the measurement positions A and B, spectroscopic measurement can be performed at a narrower pitch.

In the above method, measurement cannot be performed in the areas d ₁ and d ₂ shown in FIG. 12 (f) due to the positional relationship between the front roller 52 and the rear roller 53 and the front end portion and the rear end portion of the image bearing medium 90. . However, there is an invalid area where printing is not performed at the outer edge of the image bearing medium 90. Therefore, by associating the size of the invalid area of the image bearing medium 90 with the sizes of the areas d ₁ and d ₂ shown in FIG. 12F, the entire effective area (printable area) of the image bearing medium 90 is matched. High-precision spectroscopic measurement is possible.

  As described above, the image characteristic measurement apparatus according to the first embodiment is a sensor as an assembly of minute spectroscopic sensors that execute spectroscopic measurement at a plurality of locations with the full width of the image bearing medium. The individual spectroscopic sensor constitutes a spectrometer that obtains spectroscopic data of the number of bands corresponding to the number of pixels by receiving the dispersed diffraction image with a plurality of pixels. This makes it possible to measure the color of the entire image width with high accuracy.

  Further, by providing a moving means for relatively moving the image characteristic measuring device and the image bearing medium, it is possible to measure a plurality of locations in the conveying direction (sub-scanning direction) of the image bearing medium.

  In addition, in the conventional image characteristic measuring apparatus, there is a region where the color of the image on the image bearing medium cannot be measured accurately due to a shape variation such as deflection of the front and rear end portions of the image bearing medium. In the image characteristic measuring apparatus according to the first embodiment, by providing the optical path changing means (for example, the micromirror 24), two different locations on the image carrier medium by the single sensor (for example, the line sensor 16). Diffuse reflected light at the position (2 lines) can be acquired simultaneously. Therefore, the color of the image on the image bearing medium can be accurately obtained in the entire image bearing medium by simultaneously acquiring diffuse reflection light at two positions (two lines) with the shape variation of the image bearing medium corrected. Can be measured. In addition, by accurately measuring the color of the image, it is possible to guarantee the color over every corner of the image.

<Modification of First Embodiment>
In FIG. 12, the measurement area on the image bearing medium 90 can be maximized by matching the distance between the inner side of the front roller 52 and the inner side of the rear roller 53 and the distance between the measurement positions A and B. At this time, it is desirable to shorten the distance between the inner side of the front roller 52 and the inner side of the rear roller 53, and to increase the time during which the image bearing medium 90 is pressed by both the front roller 52 and the rear roller 53.

  As a result, a region c where a and b overlap on the image bearing medium 90 in FIG. 12F is widened, and the measurement values at the measurement positions A and B can be combined to perform spectroscopic measurement at a narrow pitch. The area can be expanded.

  By the way, when the distance between the inner side of the front roller 52 and the inner side of the rear roller 53 and the distance between the measurement positions A and B are matched, there is a problem in the arrangement of the line illumination light sources 11 and 21 in the image characteristic measuring apparatus 10 shown in FIG. May occur. That is, the irradiation light of the line illumination light sources 11 and 21 may be blocked by the front roller 52 and the rear roller 53 and cannot reach the image bearing medium 90.

  Therefore, in the image characteristic measuring apparatus 10A shown in FIG. 13, the arrangement interval (X direction) between the line illumination light source 11 and the line illumination light source 21 is shortened, and the irradiation light of the line illumination light source 11 and the irradiation light of the line illumination light source 21 are However, they reach the image bearing medium 90 after crossing each other.

  In this way, the line illumination light sources 11 and 21 are arranged so that the irradiation lights from each intersect, and light is irradiated to a measurement position farther from each line illumination light source among the two measurement positions. Thereby, even when the distance between the inner side of the front roller 52 and the inner side of the rear roller 53 and the distance between the measurement positions A and B are matched, each line illumination light source is not blocked by the front roller 52 and the rear roller 53. The image bearing medium 90 can be irradiated with light.

  That is, in the image evaluation apparatus 50 shown in FIG. 11, the measurement area on the image bearing medium 90 can be maximized by using the image characteristic measurement apparatus 10 </ b> A instead of the image characteristic measurement apparatus 10.

<Second Embodiment>
In the second embodiment, an example of an image characteristic measuring apparatus having one line illumination light source is shown. In the second embodiment, description of the same components as those of the already described embodiments may be omitted.

  FIG. 14 is a diagram illustrating an image characteristic measuring apparatus according to the second embodiment. Referring to FIG. 14, the image characteristic measuring apparatus 10 </ b> B is different from the image characteristic measuring apparatus 10 according to the first embodiment in that the line illumination light sources 11 and 21 are replaced with one line illumination light source 31 (FIG. 1). Different from reference).

  As the line illumination light source 31, for example, the same type of light source as that of the line illumination light source 11 can be used. However, the line illumination light source 31 is a light source capable of emitting light having a thickness that can irradiate the region 93 in a lump. The region 93 is a continuous region (surface) including lines 91 and 92 at both ends in the X direction on the image bearing medium 90.

Thus, even when irradiating the region 93 that includes the line 91 and 92 at both ends in the X direction at once by one line illumination source 31, in the first optical path to get the diffuse reflected light L ₁₁ from line 91, In the second optical path, the diffuse reflected light L ₂₁ from the line 92 can be acquired. As a result, the image characteristic measuring apparatus 10B has an effect that the number of parts can be reduced in addition to the effect exhibited by the image characteristic measuring apparatus 10. Of course, in the image evaluation apparatus 50 shown in FIG. 11, the image characteristic measurement apparatus 10 </ b> B can be used instead of the image characteristic measurement apparatus 10.

<Third Embodiment>
In the third embodiment, an example of an image forming apparatus having the image evaluation apparatus according to the first embodiment is shown. FIG. 15 is a diagram illustrating an image forming apparatus according to the third embodiment. Referring to FIG. 15, the image forming apparatus 80 includes an image evaluation apparatus 50 according to the first embodiment, a paper feed cassette 81a, a paper feed cassette 81b, a paper feed roller 82, a controller 83, and a scan. An optical system 84, a photosensitive member 85, an intermediate transfer member 86, a fixing roller 87, and a paper discharge roller 88 are included.

  In the image forming apparatus 80, the image carrier medium 90 transported by the guides (not shown) and the paper feed rollers 82 from the paper feed cassettes 81a and 81b is exposed to the photosensitive member 85 by the scanning optical system 84, and the color material is applied and developed. Is done. The developed image is transferred onto the intermediate transfer member 86 and then from the intermediate transfer member 86 onto the image bearing medium 90. The image transferred onto the image bearing medium 90 is fixed by the fixing roller 87, and the image bearing medium 90 formed with the image is ejected by the ejection roller 88. The image evaluation device 50 is installed at the subsequent stage of the fixing roller 87.

  As described above, according to the third embodiment, the image evaluation apparatus according to the first embodiment is mounted at a predetermined position of the image forming apparatus, thereby correcting the shape variation of the image bearing medium. The color information on the entire surface of the image can be accurately measured in the image forming apparatus. As a result, color fluctuations and color unevenness over the entire surface of the image become obvious, and image defects can be automatically corrected by feeding back the amount of fluctuation and unevenness distribution to the product.

  Further, since it is possible to acquire image information over the entire image, it is possible to store inspections and print data, and to provide a highly reliable image forming apparatus.

  Further, the image characteristic measuring apparatus according to the first embodiment has uniformity in accuracy and spectral characteristics between the spectral sensors, and the spectral sensors having substantially the same performance form an array. Therefore, it is possible to measure the measurement target and the measurement region as variable depending on whether the measurement target to be measured in the image forming apparatus is an arbitrary image output by the user or a patch image in which a plurality of relatively wide constant colors are arranged. It becomes possible.

  In addition, when the image forming apparatus is an electrophotographic system, it is possible to reduce color unevenness in the image plane by image processing such as one-scan control of the light source output of the writing scanning optical system and gamma correction before printing. It becomes. In the case where the image forming apparatus is an ink jet system, it is possible to reduce color unevenness in the image plane by directly controlling the ink discharge amount according to the head position. At the same time, it is possible to perform defect inspection on the print contents such as personal information from the brightness information of the image.

  In addition, it is possible to simultaneously perform inspection of print contents such as image quality such as color unevenness in the image plane and character information, and an image product with high image quality, high reliability, and high stability can be provided.

  The preferred embodiment has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications and replacements are made to the above-described embodiment without departing from the scope described in the claims. Can be added.

10, 10A, 10B Image characteristic measuring device 11, 21, 31 Line illumination light source 12, 14, 22 Imaging optical system 13 Aperture array 15 Diffraction element 16 Line sensor 16a, 16b, 16c Spectroscopic sensor 23 Mirror 24 Micromirror 50 Image evaluation Device 51 Belt 52 Front roller 53 Rear roller 80 Image forming device 81a Paper feed cassette 81b Paper feed cassette 82 Paper feed roller 83 Controller 84 Scanning optical system 85 Photoconductor 86 Intermediate transfer member 87 Fixing roller 88 Paper discharge roller 90 Image carrier medium 91, 92 line 93 region 130 opening 130 ₁ first opening 130 ₂ second opening

Special table 2008-518218 gazette

Claims (9)

A light irradiation means for irradiating the object with light;
First imaging means for condensing reflected light from the object of the light emitted from the light irradiation means;
Area dividing means for dividing the reflected light from the object collected by the first imaging means into a plurality of openings;
A second imaging means for condensing the reflected light from the object divided into regions through the opening;
Spectroscopic means for spectroscopically analyzing the reflected light from the region-divided object focused by the second imaging means;
Light receiving means for receiving reflected light from the object spectrally separated by the spectroscopic means,
The plurality of apertures includes a first aperture that does not include an optical path changing unit that changes the optical path of incident light on the object side, and an optical path change unit that changes the optical path of incident light on the object side. and a second opening, only including,
The reflected light from the first region of the object passes through the first opening,
The reflected light from the second area of the object is an image characteristic measuring device whose optical path is changed by the optical path changing means and passes through the second opening .   2. The image characteristic measuring apparatus according to claim 1, wherein the first opening and the second opening are regularly distributed.   3. The image characteristic measuring apparatus according to claim 1, wherein the first image forming means is image side telecentric. Having a second light irradiation means for irradiating the object with light;
The light irradiation means irradiates light to the first region of the object,
The second light irradiating means is an image characteristic measurement apparatus of any one of claims 1 to 3 for emitting light to the second region of the object. The image characteristic measurement apparatus according to claim 4 , wherein the irradiation light of the light irradiation unit and the irradiation light of the second light irradiation unit cross each other before reaching the object. The light irradiation unit, the first region and the image characteristic measurement apparatus of any one of claims 1 to 3 irradiates collectively region including the second region. The image characteristic measuring device according to any one of claims 1 to 6 ,
Moving means for relatively moving the image characteristic measuring device and the object in a predetermined direction;
Pressing means for pressing the front side and the rear side of the object in the predetermined direction,
An image evaluation device that simultaneously measures the colors of two images of the object in different predetermined directions by the image characteristic measurement device. The image evaluation apparatus according to claim 7 , wherein the color of the image is measured when both the front side and the rear side of the object are pressed by the pressing unit. An image forming apparatus including an image evaluation apparatus according to claim 7 or 8, wherein.